This is driveing me nutz! I checked every thing. I even replaced the belt tentioner. It jumps off when it wants to. It did it several times then it worked fine. now its doing it again. WHATTHE****!!!!!!

Also......I would ck the water circulater pump on the center of the engine and the water pump pullys .Maybe a bearing is going out .Ck make sure everything if tight ,brackets,Also if it chunks the belt off ya need to replace it, I would buy the Napa belts that way you can take them back get the warranted.I am turning my up to 6000-6100 at times with no problems.

Have you replaced any accessories on front or engine? If no service has been done, I would start checking each bracket holding P/S pump, Alternator, Etc. Something may have come loose and is creating a misalignment issue. I would also check the each pulley (especially crank pulley) for loose bolts also... Hope this helps.